Apparatus and method for cooling an electric motor

ABSTRACT

An improved electric motor cooling construction where the motor stator is contained within the motor housing. The motor covers and motor housing are designed to provide direct increased airflow to the motor stator, and coil windings to provide better airflow through the motor resulting in improved cooling.

FIELD OF THE INVENTION

[0001] This invention relates to cooling of electric motors. Morespecifically, the present invention relates to an apparatus and methodto improve the cooling of electric motors by creating a more evenairflow over the motor coil windings and stator laminations.

BACKGROUND OF THE INVENTION

[0002] The majority of all commercial and industrial electric fans havean electric motor. These motors generate heat from the motor windings.This heat, when excessive, can degrade overall performance and longevityof the motor. Typically fan designers try to use the “suction” on therear of the blade and blade hub to help pull the air through the rear ofthe motor towards the front. This airflow is important in providingcooling for the motor windings, however, there are many structurallynecessary elements that are part of the motors which limit the amount ofairflow that can help cool the motor.

[0003] One of these structurally necessary elements is the motorhousing. The motor housing is used to mount the bearings, which supportthe shaft for rotation. The housing also protects the windings fromdamage after the motor is assembled, and also acts as an enclosure. Thehousing has openings, the size of which is mandated by standardsorganizations such as Underwriters Laboratories. If the openings in thehousings exceed a certain mandated size, special cover materials oradditional enclosures are required. Motors housings can be castaluminum, zinc or stamped metal. Motor housings are in contact with thestator, and, in the prior art, closely surround the windings/coils,which leaves little to no area for “air flow” through the motor.

[0004] A second structural element, which limits airflow through themotor, consists of the stator and rotor. The stator consists of a stackof steel laminations which have copper magnet wire wound on them.Conventionally, the steel is normally sandwiched between the front andthe rear housings.

[0005] Looking through the rear housing, the wire and stator laminationsblock the airflow through the motor. The area of opening for airmovement through the stator is generally quite small even inrelationship to the mandated holes in the motor housings and the motorcovers. The prior art housings are so tight against the outside of thelaminations that they generally do not allow adequate airflow throughthe housings and by the coils. The two motor housings typically have agap where the stator sits, which also allows some of the air enteringthe rear motor housing to escape, thereby completely bypassing the frontcoil.

[0006] A third structural element, which effects airflow through themotor, is the outside motor cover. For safety purposes most electricmotors are surrounded by “motor covers.” Common materials for motorcovers are metal and plastic. These covers are usually aesthetic andcover any electrical materials and/or hot motor surfaces. These, motorcovers may additionally impede airflow through the motor. Motor covershave vent structures which are usually located at the rear and the frontof the motor. Venting provides an airflow path that will enter the “rearmotor cover” and flow mostly around the outside of the motor housingdrawing heat from the housings, which in turn draws heat from thestator/windings. This prior art airflow path 30, as illustrated in FIG.2, has little to no effect on the front coil area of the motor,resulting in uneven heat dissipation throughout the windings.Accordingly, the prior art airflow pattern enters the rear motor cover11 and travels mainly between the inside of the motor cover walls andthe outside of the motor housings 14 and 15. This prior art constructionand its resultant airflow does not provide adequate and even cooling ofthe motor.

[0007] The inventive design, set forth in detail below, forces a greateramount of air to be drawn into the motor housing and flow in a path thatcontacts both the front and rear windings and provides more even coolingof both the front and rear windings and the stator.

SUMMARY OF THE INVENTION

[0008] In view of the shortcomings of the prior art, the presentinvention provides a method and apparatus for improved electric motorcooling.

[0009] It has now been found that an improved electric motor coolingconstruction is available wherein the motor housing and covers draw inmore air and channel it into an air path that directly contacts themotor stator and coil windings to remove the heat and to more evenlycool the motor.

[0010] The improved electric motor comprises a first housing having afirst wall defining a first interior space, and at least one openingdisposed on a surface of the first housing; a second housing having asecond wall defining a second interior space, and at least one openingdisposed on a surface of the second housing; and a stator having aplurality of laminations a first portion of windings and a secondportion of windings, the plurality of laminations disposed substantiallywithin the first interior space and the second interior space, such thatair flows i) into the at least one opening in the first housing, ii)over the first portion of windings, substantially all an exteriorportion of the stator laminations, and the second portion of windings,and iii) out the at least one opening in the second housing.

[0011] According to another aspect of the invention, a front coverhaving openings is coupled to the surface of the second housing, and arear cover having openings is coupled to the front cover andsubstantially surrounds the first and second housings. The openings inthe rear cover are in fluid communication with the openings in firsthousing, and the openings in the front cover are adjacent and in fluidcommunication with the openings in the second housing.

[0012] According to a further aspect of the invention, the stator issubstantially square.

[0013] According to yet a further aspect of the invention, the at leastone opening in the first housing is a first plurality of openings andthe at least one opening in the second housing is a second plurality ofopenings, at least a portion of the first plurality of openings and atleast a portion of the second plurality of openings in respective planessubstantially parallel to one another.

[0014] According to another aspect of the invention, the motor housingsare in contact with the stator and have airflow channels therebetween.

[0015] According to yet another aspect of the invention, the stator issubstantially round.

[0016] According to still another aspect of the invention, the frontmotor cover contacts the front motor housing to seal off airflow,forcing air through the motor.

[0017] According to yet a further aspect of the invention, the front andrear motor housings have a reduced gap therebetween so that airflow isinhibited from escaping from between the motor housings.

[0018] According to another aspect of the invention, the electric motorhas a reduced operating temperature and a more even cooling of thestator windings and laminations.

[0019] These and other aspects of the invention are set forth below withreference to the drawings and the description of exemplary embodimentsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention is best understood from the following detaileddescription when read in connection with the accompanying drawing. It isemphasized that, according to common practice, the various features ofthe drawing are not to scale. On the contrary, the dimensions of thevarious features are arbitrarily expanded or reduced for clarity.Included in the drawing are the following Figures:

[0021]FIG. 1 is an exploded perspective view of a prior art electricmotor assembly;

[0022]FIG. 2 is a sectional view of the prior art motor assembly of FIG.1;

[0023]FIG. 3A is a perspective view of an electric motor incorporating afirst exemplary embodiment of the present invention;

[0024]FIG. 3B is a perspective view of an electric motor incorporating asecond exemplary embodiment of the present invention;

[0025]FIGS. 3C and 3D are sectional views illustrating details of theexemplary embodiment of FIG. 3B;

[0026]FIG. 4 is a sectional view of the motor of FIGS. 3A and 3B;

[0027]FIG. 5 is a chart showing the performance characteristics of aprior art electric motor;

[0028]FIG. 6 is a chart showing the performance characteristics of anelectric motor which incorporates an exemplary embodiment of the presentinvention, and;

[0029]FIG. 7 is an illustration of an oscillating fan incorporating anexemplary embodiment of the present invention.

[0030] It should, of course, be understood that the description anddrawings herein are merely illustrative and that various modificationsand changes can be made in the structures disclosed without departingfrom the spirit of the invention. Like numerals refer to like partsthroughout the several views.

DETAILED DESCRIPTION

[0031] When referring to the preferred embodiment, certain terminologywill be utilized for the sake of clarity. Use of such terminology isintended to encompass not only the described embodiment, but alsotechnical equivalents which operate and function in substantially thesame way to bring about the same result.

[0032] Referring now more particularly to the drawings and FIGS. 1 and 2thereof, a prior art electric motor assembly 10 is therein illustrated.

[0033] As shown in FIG. 1, motor assembly 10 includes rear cover 11,front cover 12 of a generally circular configuration, with motor 50contained therein.

[0034] Motor 50 includes front and rear motor housings 15 and 14,respectively, which are in contact with and are secured to the outsidesurfaces of motor stator 17, in a conventional manner, retaining ittherebetween, such as by screws 18 extending into spaced bosses 20, onmotor housings 14 and 15.

[0035] Motor stator 17 is of square configuration and extends outsidemotor housings 14 and 15.

[0036] Referring now to FIG. 2, motor assembly 10 is also provided withrotor (not shown) and output shaft 22, which has a hub 23 of fan bladeassembly 24 secured thereto in a conventional well known manner. Motorstator 17 includes a plurality of laminated sheets of steel 25, withrear coil windings 26, and front coil windings 27, secured thereto in awell known manner.

[0037] Referring again to FIG. 2, the airflow pattern for cooling motor50 is illustrated by curved lines 30, which show air entering throughopenings 31 in rear cover 11, over a motor capacitor 32, over theexterior of rear motor housing 14, over the exterior of front motorhousing 15 and exiting through openings 35 in front cover 12 (best shownin FIG. 1).

[0038] As is clearly shown in FIG. 2, airflow 30 does not directlycontact the laminated sheets 25, and the rear coil windings 26 and thefront coil windings 27 to provide cooling. Rather, airflow 30ineffectively attempts to draw heat away by contacting front motorhousing 15 and rear motor housing 14.

[0039] Referring now more particularly to FIGS. 3A and 4, a fan motorassembly 300 incorporating a first exemplary embodiment of the presentinvention is shown. As shown in FIG. 3A, fan motor assembly 300 includesrear cover 101, rear motor housing 102, front cover 104, and motor 100.Each of front and rear motor housing 103, 102 have at least onerespective opening (122 as shown in FIG. 3a for rear motor housing 102)therein to allow for the passage of air therein (explained in detailbelow with respect to FIG. 4). Opening 122 may be formed in a variety ofshapes and orientations, such as slots formed circumferencially and/orradially, or circular openings, for example.

[0040] Motor 100 includes rear motor housing 102 and front motor housing103 defining interior spaces 132 and 133, respectively. The front andrear motor housings 103 and 102 are fastened together by fasteners 105,such as screws, which may extend through bosses 106 in rear motorhousing 102 into bosses 107 in front motor housing 103, securing themotor housings in fluid tight relation with one another. Motor housings102 and 103 are preferably of cast or stamped metal such as aluminum,zinc or steel. Alternatively, either or both motor housings 102, 103 maybe formed from a polymer, if desired.

[0041] Rear cover 101 is secured to the rear motor housing 102 by afastener 108 (best shown in FIG. 4), such as a screw, engaged in boss109 which is in turn coupled to housing 102. Front and rear motor covers104 and 101 are preferably of metal or plastic.

[0042] Referring now to FIG. 4, motor stator 110 is provided, of agenerally square configuration, with a plurality of laminated sheets ofsteel 111, with rear coil windings 112, and front coil windings 114secured thereto in a well known manner. In this exemplary embodiment,motor stator 110 is contained substantially within interior spaces 132,133 of motor housing 102 and 103, with only corners 127 of stator 110extending beyond the confines of motor housing 102 and 103 (best shownin FIG. 3A). Motor 100 has a rotor 113, output shaft 134, and hub 115 offan blade assembly 116 secured thereto.

[0043] Front cover 104 has inside and outside rims 117 and 118, whichreceive rear cover 101 therebetween, to couple front cover 104 to rearcover 101 and form a seal between front cover 104 and rear cover 101. Asshown in FIG. 4, front cover 104 is in close contact with the frontmotor housing 103 and is attached thereto in a conventional manner,using screws, for example (not shown).

[0044] Referring now to FIG. 3B, fan motor 200 incorporating a secondexemplary embodiment of the present invention is shown. As shown in FIG.3B, the significant differences between the first and second exemplaryembodiments is the containment of the entirety of stator 210 withininterior 232, 233 of motor housings 202, 203, respectively, formingairflow cavity 234 between the inner walls of motor housings 202, 203and stator 210. This is best illustrated in FIG. 3C. Similar to thefirst exemplary embodiment, the front and rear motor housings 203 and202 are fastened together by fasteners 105, such as screws, which mayextend through bosses 206 in rear motor housing 202 into bosses 207 infront motor housing 203, securing the motor housings in fluid tightrelation with one another.

[0045] In one version of this exemplary embodiment, stator 210 issubstantially round and attached to at least one of housings 202, 203using conventional means, such as staking through the walls of either orboth housings 202, 202, press fit within either or both housings 202,202, or stops incorporated within interior spaces 132 and 133 of themotor housings, for example. Alternately, and as shown in FIG. 3D,stator 310 may be substantially square.

[0046] In an exemplary embodiment of the present invention, motor 100may be a permanent split capacitor (PSC) motor having any of a varietyof pole configurations, such as 4 poles and 6 poles. The invention isnot so limited, however, and it is contemplated that motor 100 may be ofother types, such as a shaded pole motor, for example.

[0047] As shown in FIG. 4, air, depicted by air flow lines 128, is drawntoward and enters motor 100 by action of fan blade 116, through openings120 in rear cover 101, and through openings 122 in rear motor housing102, over and in contact with rear coil windings 112, the exteriorportions of laminated sheets 111, front coil windings 114, exitingthrough openings 125 in front housing 103, and finally out the frontcover 104 through openings 126, thereby drawing heat out of fan motor100. This improved airflow is substantially identical in each of the twoexemplary embodiment described above.

[0048] Referring now to FIG. 5, a fan motor, such as motor 50 was testedfor efficiency and measured temperature. As shown in FIG. 5, at column502, the heat distribution with a conventional cooling construction wasvery uneven, with an 11.3° C. differential between front coils 27 andrear coils 26.

[0049] In FIG. 6, motor 100 was tested where the only difference betweenmotor 100 and motor 10 was the improved cooling provided by motorhousings 102, 103, front cover 104 and rear cover 101. As shown in FIG.6, at column 602, the temperatures of the front and rear coil windings114 and 112 were the same and were significantly lower than thetemperatures recorded for motor 10 by greater than 19° C. for the rearcoils and by greater than 30° C. for the front coils. As shown in FIG.7, it is contemplated that this improved motor assembly 300 may be usedin an oscillating fan 700, for example.

[0050] Although the invention has been described with reference toexemplary embodiments, it is not limited thereto. Rather, the appendedclaims should be construed to include other variants and embodiments ofthe invention, which may be made by those skilled in the art withoutdeparting from the true spirit and scope of the present invention.

1-23. (Canceled)
 24. An electric fan motor comprising: a first motorhousing having at least one inlet opening disposed on a surface of thefirst motor housing; a second motor housing having at least one outletopening disposed on a surface of the second motor housing; and a statorcomprising: i) a plurality of laminations formed in a stack andsubstantially disposed within at least one of the first motor housingand the second motor housing, the stack having a plurality of passagesformed therethrough, ii) windings passing within at least a portion ofsaid plurality of passages, iii) a first portion of the windingsdisposed on a first side of the stack and substantially within the firstmotor housing, and, iv) a second portion of the windings disposed on asecond side of the stack and substantially within the second motorhousing, wherein the at least one inlet opening is in fluidcommunication with the at least one outlet opening and air flows i) intothe at least one inlet opening, ii) over the first portion of windings,substantially all of an exterior portion of the plurality oflaminations, and the second portion of windings, and iii) out the atleast one outlet opening.
 25. An electric motor according to claim 24further comprising, a motor cover substantially enclosing the first andsecond motor housings therein, the motor cover including: i) a firstcover coupled to the second motor housing, the first cover having atleast one opening in a surface thereof, the at least one openingadjacent and in fluid communication with the at least one opening in thesecond motor housing, and ii) a second cover coupled to the first coverand substantially surrounding the first and second motor housings, thesecond cover having at least one opening in a surface thereof, the atleast one opening adjacent and in fluid communication with the at leastone opening in the first motor housing.
 26. An electric motor accordingto claim 25, wherein the first and second covers are formed from atleast one of a metal and a polymer.
 27. An electric motor according toclaim 25, wherein the second cover is coupled to a portion of the firstmotor housing.
 28. An electric motor according to claim 25, furthercomprising means for sealing the first cover to the second cover.
 29. Anelectric motor according to claim 24 further comprising, a motor coversubstantially enclosing the first and second motor housings therein, themotor cover including: i) a first cover coupled to the second motorhousing and substantially surrounding the first and second motorhousings, the first cover having at least one opening in a surfacethereof, the at least one opening adjacent and in fluid communicationwith the at least one opening in the second motor housing, and ii) asecond cover coupled to the first cover, the second cover having atleast one opening in a surface thereof, the at least one openingadjacent and in fluid communication with the at least one opening in thefirst motor housing.
 30. An electric motor according to claim 24,wherein the first and second motor housings are formed from a metal. 31.An electric motor according to claim 24, wherein the stator issubstantially square.
 32. An electric motor according to claim 24,wherein the stator is substantially round.
 33. An electric motoraccording to claim 24, wherein an end portion of the stator is coupledto at least one of the first and second motor housings.
 34. An electricmotor according to claim 24, wherein the at least one opening in thefirst motor housing and the at least one opening in the second motorhousing are in respective planes that are substantially parallel to oneanother.
 35. An electric motor according to claim 24, furthercomprising: a rotor at least partially disposed adjacent the stator, ashaft coupled to the rotor and extending through the second motorhousing such that an end portion of the shaft is positioned external thesecond motor housing; and a fan blade coupled to the end portion of theshaft and adjacent the at least one outlet opening.
 36. An oscillatingfan incorporating the electric motor according to claim
 24. 37. Anelectric fan motor comprising: a first motor housing comprising: i) afirst wall defining a first interior space, ii) at least one openingdisposed on a surface of the first motor housing, and iii) a matingsurface; a second motor housing comprising: i) a second wall defining asecond interior space, ii) at least one opening disposed on a surface ofthe second motor housing, and iii) a mating surface; and a statorcomprising: i) a plurality of laminations coupled to a portion of themating surface of the first motor housing and a second surface coupledto the mating surface of the second motor housing, ii) a first portionof windings disposed within only the first interior space, and iii) asecond portion of windings disposed within only the second interiorspace, wherein the air flows i) into the at least one opening in thefirst motor housing, ii) over the first portion of windings,substantially all of an exterior portion of the plurality of statorlaminations, and the second portion of windings, and iii) out the atleast one opening in the second motor housing.
 38. An electric motorcomprising: a first motor housing comprising: i) a first wall defining afirst interior space, and ii) at least one opening disposed on a surfaceof the first motor housing; a second motor housing comprising: i) asecond wall defining a second interior space, and ii) at least oneopening disposed on a surface of the second motor housing; and a statorcomprising i) a plurality of laminations, ii) a first portion ofwindings and iii) a second portion of windings, the plurality oflaminations disposed substantially within a space defined by acombination of the first interior space and the second interior space,wherein air flows i) into the at least one opening in the first housing,ii) over the first portion of windings, substantially all of an exteriorportion of the plurality of stator laminations, and the second portionof windings, and iii) out the at least one opening in the secondhousing.
 39. An oscillating fan incorporating the electric motoraccording to claim
 38. 40. An electric fan motor comprising: rotormeans; stator means for providing an electro-magnetic force to the rotormeans; first motor housing means for housing therein only a firstportion of the stator means; second motor housing means for housingtherein only a second portion of the stator means; and ventilation meansfor providing airflow i) into the first motor housing means, ii) over atleast substantially all of an exterior portion the stator means, andiii) out of the second motor housing means.
 41. An electric motoraccording to claim 40 further comprising: cover means for covering thefirst and second motor housing means; and sealing means for forming aseal in the cover means, wherein the airflow passes into a first portionof the cover means, through the first and second motor housing means andout a second portion of the cover means.
 42. An electric motor accordingto claim 40, wherein the motor is a permanent split capacitor motor. 43.An electric motor according to claim 40, wherein the motor is a shadedpole motor.
 44. A method for cooling an electric motor having a statorwith a plurality of laminations and motor windings, the methodcomprising the steps of: providing a first motor housing with a firstsurface, and defining a first interior space; providing a second motorhousing with a second surface, and defining a second interior space;enclosing only a first portion of the motor windings within the firstinterior space; enclosing only a second portion of the motor windingswithin the second interior space; enclosing substantially all of theplurality of stator laminations within both the first interior space andthe second interior space; and providing airflow i) into the firstsurface of the first motor housing, ii) over substantially all of anexterior portion of the plurality of stator laminations, iii) oversubstantially all of the motor windings, and iv) out of the secondsurface of the second motor housing.
 45. An electric fan motorcomprising: a first motor housing having at least one inlet openingdisposed on a surface of the first motor housing; a second motor housinghaving at least one outlet opening disposed on a surface of the secondmotor housing; and a stator comprising: i) a plurality of laminationsformed in a stack and substantially disposed within at least one of thefirst motor housing and the second motor housing, the stack having aplurality of passages formed therethrough, ii) windings passing withinat least a portion of said plurality of passages, iii) a first portionof the windings disposed on a first side of the stack and adjacent anend wall of the first motor housing, and, iv) a second portion of thewindings disposed on a second side of the stack and adjacent an end wallof the second motor housing, wherein the at least one inlet opening isin fluid communication with the at least one outlet opening and airflows i) into the at least one inlet opening, ii) over the first portionof windings, substantially all of an exterior portion of the pluralityof laminations, and the second portion of windings, and iii) out the atleast one outlet opening.
 46. An electric fan motor comprising: a firstmotor housing comprising: i) a first wall defining a first interiorspace, ii) at least one opening disposed on a surface of the first motorhousing, and iii) a mating surface; a second motor housing comprising:i) a second wall defining a second interior space, ii) at least oneopening disposed on a surface of the second motor housing, and iii) amating surface; and a stator comprising: i) a plurality of laminationscoupled to the first motor housing and the second motor housing, and ii)a first portion of windings and a second portion of windings disposedsubstantially within at least one of the first and second motorhousings, wherein the air flows i) into the at least one opening in thefirst motor housing, ii) over the first portion of windings,substantially all of an exterior portion of the plurality of statorlaminations, and the second portion of windings, and iii) out the atleast one opening in the second motor housing.